1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.
In this specification, a semiconductor device generally means a device which can function by utilizing semiconductor characteristics, and an electro-optic device, a semiconductor circuit, and electronic equipment are all semiconductor devices.
2. Description of the Related Art
Transistors in which an active layer is formed using a semiconductor thin film which is formed over a substrate having an insulating surface are widely used in electronic devices such as integrated circuits (ICs) and image display devices (display devices). A silicon-based semiconductor material is widely known as a material for a semiconductor thin film applicable to a transistor. As another material, an oxide semiconductor has been attracting attention.
For example, a transistor whose active layer includes an amorphous oxide including indium (In), gallium (Ga), and zinc (Zn) is disclosed (see Patent Document 1).